1. Field of the Invention
The present invention relates to respiratory interface devices for transporting a gas to and/or from an airway of a user which include, but not limited to, a mask having a flexible faceplate or patient contacting cushion, and in particular to a flexible respiratory interface device that is supported by a brace and having a flexible membrane assembly disposed between the mask and the brace body.
2. Description of the Related Art
A variety of respiratory masks are known which cover the areas surrounding the nose and/or mouth of a human user and that are designed to create an effective fit against the user's face. Typically, gases can be provided at a positive pressure within the mask for consumption by the user. The uses for such masks include high altitude breathing (aviation applications), swimming, mining, fire-fighting, and various medical diagnostic and therapeutic applications.
One requisite of many of these masks, particularly medical respiratory masks, is that they provide an effective fit against the user's face and that the mask contours with the user's face to limit or prevent leakage of the gas being supplied. A common type of mask incorporates a single-piece faceplate or a two-piece faceplate, having an upper portion (e.g., to cover the nasal portion of a human user's face) and lower portion (e.g., to cover the mouth portion of a human user's face) that are unitary or coupled together by a flexible member. See, for example, U.S. Patent Pub. 2011/0232647 which is incorporated by reference.
The respiratory masks that are known also have a sealing surface or cushion around the periphery of the mask to seal against the user's face. The cushion is typically attached to the faceplate. Such masks have performed well when the fit is good between the contours of the seal surface and the corresponding contours of the user's face. This may occur, for example, if the mask is properly oriented and provides a good fit against the user's face and the mask contours with the user's face. If the mask is not properly oriented or if the fit is not good, there will be gaps in the mask-to-face interface resulting in gas leaking from the mask at the gaps. Considerable force will be required to compress the mask member to close the gaps and attain a satisfactory seal in those areas where the gaps occur.
Typically, this required force will be provided by straps that are connected to the mask or to a brace assembly to which the mask is coupled. Such force is undesirable because it produces high pressure points elsewhere on the face of the user where the mask contour is forcibly deformed against the face to conform to the user's facial contours. This will produce considerable user discomfort and possible skin irritation and breakdown anywhere the applied force exceeds the local perfusion pressure, which is the pressure that is sufficient to cut off surface blood flow.
For example, it is not uncommon to have a gap between the cushion and the user's face at the bridge of the nose or adjacent the bridge of the nose. When such a gap occurs, the user may adjust the straps by tightening or loosening the straps, as discussed above, or by moving the position of the straps relative to the user's face. Typically, the user would move the straps to a higher position on their face. This adjustment, however, places the straps closer to the user's eyes, which is generally considered to be uncomfortable. Alternatively, the respiratory interface device may be provided with additional straps so as to allow for better positioning of the respiratory interface device relative to the user's face. Additional straps, however, are also generally considered to be uncomfortable.
When a respiratory mask utilizes a brace assembly, the brace assembly is, typically, directly coupled to the mask in a fixed orientation. In this configuration, the bias created by the straps passes through the coupling between the brace assembly and the mask. Thus, the orientation of the mask relative to the user's face is affected by the bias on the brace assembly. For example, assuming there are two upper straps and two lower straps, if the user tightens the upper straps there will be a greater bias on the upper portion of the brace assembly and therefore the upper portion of the mask will be more biased toward the user's face. That is, the mask will not be properly oriented in that the mask is, essentially, tilted upwardly. This may create a gap along the lower edge of the mask sealing surface. The user must then tighten the lower straps to compensate. The user, however, may overcompensate thereby creating a gap along the upper edge of the mask sealing surface. Such strap adjustments may continue and may result in a mask that is too tight or otherwise uncomfortable.
Accordingly, a need exists to provide a respiratory interface device capable of providing a more complete seal between the patient's face and the cushion without having to adjust the straps and/or adjust the straps in a manner that is uncomfortable for the user. Further, a need exists to provide a respiratory interface device capable of automatically orienting the mask in a proper orientation.